This document pertains in general to systems that sample signals, and in particular to systems that sample and compare multiple signals.
Integrated circuits typically communicate with other integrated circuits on wires that are part of a xe2x80x9cbus.xe2x80x9d A typical bus includes many wires, or circuit board traces, connecting multiple integrated circuits. Some buses are xe2x80x9cunidirectional,xe2x80x9d because signals only travel in one direction on each wire of the bus. Other buses are xe2x80x9cbi-directional,xe2x80x9d because signals travel in more than one direction on each wire of the bus. In the past, most bi-directional buses were not xe2x80x9csimultaneously bi-directional,xe2x80x9d because multiple signals did not travel on the same wire in opposite directions at the same time; instead, the bus was shared over time, and different signals traveled in different directions at different points in time. Some newer buses are xe2x80x9csimultaneous bi-directionalxe2x80x9d buses. Simultaneous bi-directional buses allow data to travel in two directions on a single wire at the same time.
Receivers coupled to simultaneous bi-directional buses receive signals that include multiple components. For example, a receiver may intend to receive a signal transmitted from a driver on an opposite end of a bus, but the signal actually received is the superposition of the signal transmitted from the opposite end, and a near-end signal driven by a driver that is paired with the receiver on the near-end of the bus. In order for the receiver to receive the intended signal, the received signal is typically sampled, and the near-end signal is subtracted from the sampled signal.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for a method and apparatus to provide signal sampling and subtraction mechanisms.